Telephone system



v 0a. 22, 1940. c, E BEALE 2,218,571

TELEPHONE SYSTEM Filed April 5, 193 2 Sheets- Sheet 1 Locm.

Loom.

INVENTOR HARLES Eouuuo BEALE ATTY.

Oct. 22, 1940. c, BEALE TELEPHONE SYSTEM Filed April 5, 193'? 2Sheets-Sheet 2 v INVENTOR y EDMUND BM ATTY Patented Oct. 22, 1940 UNITEDSTATES PATENT OFFICE TELEPHONE SYSTEM Charles Edmund Beale, Liverpool,England, as-

signor to Associated Telephone & Telegraph Company, Chicago, 111., acorporation of Delaware Application April 5,1937, Serial No. 134,991 InGreat Britain May 18, 1936 6 claims. (01. 179-71) 10 minimum ofdifllculty.

According to the invention in a telephone systemincluding a plurality ofexchanges and provided with arrangements for time meteringfthe timingequipment is located at a central point and the metering equipment atthe originating exchange is operated by alternating current sig nalstransmitted over the speaking leads in series during conversation.

The invention will be better understood from the following descriptionof one. method of'carry ing it into effect,reference being had tothefaccompanying drawings comprising Figs, 1 and 2.

Fig. 1 shows sufiicient of the trunking arrangements of a typicalmulti-office area to enable the application of the invention to beunderstood",

only the equipment involved in outgoing calls to central or so-calledtandem exchange, M a main exchange, S a satellite exchange and SS .2;subsatellite exchange. Fig. 2 shows the elements of the speechtransmission circuit between a calling sub-satellite subscriber and thetiming group TG which is interposed between the central'exchang'e and along junction to a distant exchange. The

comparativelyexpensivetiming groups need only beassociate'd with thoseroutes which" merit the provision of timing facilitiesf Suff cient ofdiscriminating final selector repeater DFSR is also shown to enable theoperation of the metering 40 relay resetting group -MRRG enclosed inltheMRRG may be added to existing exchange switches in any convenient mannerwhile in new exchanges it may be incorporated on the switches concerned.

y Referring now to the trunking diagramFi g. 1,

an outgoing call from asub-satellite subscriber to a distant exchangewill first be described. When the subscriber removes his receiver, he isconnected via the linefinder LE toa discriminating final selectorrepeater DFSR fwhich causes thejunction hunter JH to select an incomingdiscriminating selector repeater DSR at the satellite exchange 5 andthis in turn causes its junc- 55 tionhunter J H to select a first codeselector FCS idle register controller. RC which stores the digits dottedrectangle to be'understood. The group inthe main exchange. In responseto-the digits dialled, discrimination takes place in the discriminatingswitches with the effect in this instance that the junctions to main areretained, and the discriminating switches function only as impulserepeaters thereby preventing access to subsequent local switches ateither the satellite or sub-satellite exchanges. On seizure of the firstcode selector, a register controller hunter RCH selects an dialled and.retransmits .them after translation in the well-known manner to actuatethe first code selector and subsequent switches to route the'call overthe outgoing junction to its destination at the distant exchange. Aspecial timing group TC is interposed between the central exchangeselector repeater SR and the outgoing junction and this may givefacilities for discrimination, alternating current dialling and the likein addition to time metering. v p

Referring now to the circuit diagram Fig. 2, it will be understood thatwhen the called subscriber answers, the shunt field relay D in DFSR willbe operated in the well-known manner and at arma- .ture d2 it completesthe starting circuit for the meter delay set. This latter piece ofapparatus a distant exchange being shown. C denotes a comprises relaysDA and DB which are operated by so-called, S and Z pulse cams which arearranged to supply battery pulses with a definite timev relation to twocorresponding leads. Upon 30 reception of the next 5. pulse, relay DAwill be operated over its lower winding and prepares a circuit atarmature 11113 for relay DB which'operates afterthe appropriate timeinterval from the Z pulse in series with theupper winding of relay 35 lI its upper winding in series with the lower winding of relayDB for theduration of the Z pulse; During the application of the Z. pulse themetering relay, (not shown) is impulsed one or more times in knownmanner, according to the zone fee required, and at armature 7'! extendsbooster battery pulses over the P conductor to actuate the subscribersmeter MTR accordingly. Atthe cessation ofthe Z pulse, relay restores andprevents any further operation of the metering relay, while relay DBremains operated in series with the junction switching relay K and thejunction hunter magnet J HM since its upper winding is no longershort-circuited at armature (1123. Both relays P and K remain operatedin series with the upper winding of relay DB.

It will be understood that on the reply of the wanted party a timingdevice in the group TG is set into operation. This device mayconveniently take the form of a small self-starting inductionsynchronous motor drlven off the alternating current supply used forlong distance dial-.

ling purposes or the more conventional uni-directional switch stepped byearth pulses at tensecond intervals may be used. 1

Towards the end of the predetermined unit conversational period it isarranged that a pippip-pip warning signal at a frequency of the order of800 cycles is returned to the calling party by way of the generator Yand condenser QB. A short interval ensues and at the end of this perioda pulse of low frequency alternating current of for instance 50 cyclesis sent back by way of the generator X and condenser QA in order tooperate relay AC and reset the meter relays in DFSR. The latter pulse isapplied for an appreciable period which is of the order of fiftymilli-sec0nds in order to ensure that the meter relays are resetproperly and it is of a low frequency so as not to cause anyinconvenience to the calling subscriber. Should he not desire tocontinue the conversation, it is necessary for him to restore hisreceiver during the grace period or otherwise he will be charged for afurther conversational period. Relay AC is bridged across the line atDFSR in the sub-satellite exchange by way of a suitable low-pass filterF which renders the relay responsive only to the low frequency signalpulse and reduces the speech transmission loss to a minimum. Thearrangement of rectifiers MRA to MRD enables an ordinary telephone relayto respond satisfactorily to alternating current whilst the full- Waverectifier arrangement ensures maximum efiiciency. Relay AC willtherefore be operated for the duration of the low frequency pulse and atarmature acl it provides an earth to hold relays P 'and K and to shuntdown relay DB which when it restores to normal short-circuits its ownholding winding at armature db3. 'At the conclusion of the pulse, relayAC restores and relays P and K remain held from earth over armatures bland 11123 while since relay D is still operated, relays DA and DB willagain be operated in the same manner as before over the S and Z leadsand will cause a further set of registrations to be effected on thesubscribers meter. Preferably, during the extension of the low frequencyrepeat-metering pulse from the group TG, the through connection to thedistant exchange will be disconnected and a holding loop will beprovided to hold the distant train of switches. This ensures that allthe signalling current is directed back towards the signal receivingequipment thereby maintaining the efiiciency of the scheme at a maximum.Referring again to thetrunking diagram, it will be seen that a meteringrelay resetting group MRRG is associated with the satellite exchangediscriminating selector repeaters serving local subscribers while in themain and central exchanges the first code selectors serving localsubscribers *areequipped likewise. Since the above mentioned switchesvare all equipped with similar DA and DB relay arrangements, timemetering can be effected in a precisely similarmanner to that describedfor the sub-satellite case. It will be noticed however that with theequipment shown repeat metering will only take place on calls which passthrough the central exchange.

Iclaim:

1. In a telephone exchange system having means for extending a call froma calling subscribers line in a local exchange to a called subscribersline in a distant exchange by way of a central exchange and trunk linesconnecting said exchanges, a message register associated with saidcalling line, means in said local exchange for initially operating saidregister a predetermined number of times when said connection is firstestablished, means in said central exchange for transmitting alternatingcurrent to said local exchange over said trunk line upon the terminationof each unit period of time during which said connection is maintained,and means in said local exchange responsive to said current forreoperating said register.

2. In a telephone exchange system having means for extending aconnection from a calling subscriber in a first exchange to a calledsubscriber in a second exchange by way of a third exchange over a trunkline connecting said first and third exchanges, a message registerassociated with said calling subscribers line, and means for operatingsaid register a predetermined number of times for each unit period oftime during which said connection is maintained, said means comprising atiming group in said third exchange adapted to periodically connect analternating current of a particular frequency to the conductors of thetrunk line in series and a metering relay group in said first exchangeadapted to respond only to said particular frequency of alternatingcurrent, said particular frequency being such as not to interfere withconversation between said subscribers.

3. In a telephone system having means for extending a connection from acalling subscriber in a first exchange to a called subscriber in asecond exchange by Way of a third exchange over a trunk line connectingsaid first and third exchanges, a message register associated with saidcalling subscribers line, a metering relay group in said first exchangefor initially operating said register a predetermined number of timeswhen said connection is established, and means for causing said meteringrelay group to operate said register a predetermined number of times foreach unit period of time during which said connection is maintained,said last means comprising a timing group in said third exchange adaptedto periodically connect an alternating current of a particular frequencyto the conductors of the trunk line in series and means in said meteringrelay group adapted to respond only to said particular frequency ofalternating current.

4. In a telephone system having means for extending a connection from acalling subscriber in a first exchange to a called subscriber in asecond exchange by way of a third exchange over a trunk line connectingsaid first and third exchanges, a message register associated with saidcalling subscribers line, a metering relay group in said first exchange,means in said metering relay group for initially operating said registerwhen said connection is established, and means for causing said meteringrelay group to operate said register a predetermined number of times foreach unit period of time that said connection is maintained, said lastmeans comprising a timing group in said third exchange adapted toperiodically connect an alternating current of a particular frequency tothe conductors of the trunk line in series, a relay in said meteringrelay group responsive only to said particular frequency of alternatingcurrent and normally disconnected from said trunk line, and means forconnecting said relay to said trunk line responsive to the operation ofsaid means in said metering relay group.

5. In a time metering arrangement for a telephone exchange system, amessage register, means including a first relay and a second relay foroperating said register, means controlled by said second relay fordeenergizing said first relay,

time controlled means including a source 01 alternating current forshort-circuiting and thereby deenergizing said second relay, and meansfor sequentially reoperating said relays.

6. In a time metering arrangement for telephone systems, a messageregister, a first relay, a second relay, means for operating said firstrelay, means for operating said second relay only in case-said firstrelay is operated, means for operatingsaid register only while both ofsaid relays are operated, time controlled means including a source ofalternating current for deenergizing' said second relay, meanscontrolled by said second relay for deenergizing saidfirst relay, andmeans for sequentially reoperating said relays.

CHARLES EDMUND BEALE.

